<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>基本选择器</title>
    <style>
        .cls{
            color: red;
        }
        div{
            color: aqua;
        }
        #c{
            color: blueviolet;
        }
        #d{
            color: deeppink;
        }

    </style>
</head>
<body>
<div class="cls">div1</div>
<div>div2</div>
<div id="d">div3</div>
<div class="cls" id="c">div4</div>
</body>
</html>